M2794.006900 D E S I G N F O R M A N U F A C T U R I N G

Week 9, November 02

Manufacturing Processes

1. Subtractive Processes

Fall 2017

Professor Sung-Hoon Ahn

Department of Mechanical and Aerospace Engineering

Seoul National University

2

Outline

Multi-scale fabrication

Subtractive processes

Additive processes

Mechanical machining

Introduction

DFM: Micro machining (drilling and milling)

Laser machining

Introduction

DFM: Laser machining

Focused ion beam (FIB) fabrication

Introduction

DFM: FIB

Conclusions

3

Multi-scale fabrication

Scale Example Additive process Subtractive process

macro/meso

(100 mm)

10-1

Rapid

Prototyping

Precision

machining

micro

(100 mm)

10-4

Cold spray Laser machining

nano

(100 nm)

10-7

Nano particle

deposition

AFN printing

Focused

ion beam

Deposition

Pow-der

Virus

Mobile phoneCD-ROMMouse

ProteinSmoke

Today’s class

4

#1 Precision machining (정밀가공)

Micro tool(Material: HSS & TiN coating)

High speed spindle (43,000 rpm)

Precision micro stage

(1mm resolution)

Micro-wall

Machining process of 3-axis micro-stage

• Type : Subtractive

• Scale : 100 mm~ 100 mm

• Material : metal, polymer, etc

• Characteristic: High speed spindle, precision stage, micro-tool

Micro-rotor

5

#2 Laser machining (레이저 가공)

Schematics of laser machining system

Scan area & stage

xy

z

Stage

(3-axis)

Beam header

(galvanometer,

2-axis)

Machining process

Light guide Cell phone key pad

• Type: Subtractive

• Scale : tens of mm ~ several mm

• Material : metal, polymer, ceramic

• Characteristics : no tool-tip change

6

#3 Focused ion beam (FIB) (집속이온빔)

Micro-Tool Micro/Nano Probe

FIB Milling Process

• Type: hybrid (Additive + Subtractive)

• Scale: 10 nm ~ 100 mm

• Metal: all solid

• Characteristics : ultra precision, direct writing

• Cost : 200,000 won / hr.

Incident Ion

Sputtered Particle

(Ion, Neutron, Electron)

Focused ion beam system

Ion-Solid Interaction

7

Process envelope

Ad

dit

ive

Su

btr

acti

ve

AFN printing

-metal, ceramic

8

Machining (기계가공)

Machining is the broad term used to describe removal of material

from a workpiece.

Cutting (절삭가공)

Abrasive processes (입자가공)

Advanced machining processes (특수기계가공)

9

High speed machining

10

High speed machining

11

Cutting processes

12

Lathe

(http://youtube.com/watch?v=r_KUIx3aBhQ)(x2 Speed)

13

Turning (선삭)

(mm)cut ofdepth :

(mm/rev) feed :

(m/min) speed cutting:

Where

w

f

V

Vfw removal of Rate

14

Lathe-round shape

15

Lathe components (선반)

(심압대 )

(주축)

(가로이송대)

(왕복대)

16

Drill

(생크길이)

(선단각)

홈

17

DOC

DOC

WOC

WOC

Milling

Depth of Cut (DOC)

Width of Cut (WOC)

Slab milling (평밀링)

Conventional Milling (up

milling, 상향절삭)

Recommended, clean

surface before machine

Climb Milling (down milling,

하향절삭)

Efficient cut (larger chip)

Less chatter

Production work

18

Material removal by milling

Cutting speed (m/min)

V = pDN

(D : diameter of cutter(m), N : rotational speed of the cutter(rpm))

Material Removal Rate (MRR)

MRR = WOC * DOC * f

f = feed rate (mm/min) = n * N * t

(n: number of tooth, t : feed per tooth,

N : rotational speed of the cutter)

Example

V = 50 m/min, t = 0.1 mm/tooth, number of tooth (n)= 2,

D = 4 mm, DOC = 0.2, WOC = 3, Cutter RPM (N) =

50000/(πx4) = 3979

f = 2 *3979 * 0.1 = 796 mm/min, MRR = 3* 0.2 * 796 = 4776

mm3/min

Cutting Tool

- cross section

0.25 μm

1 mmDiameter

of cutter

Feed per

tooth

19

Sources of Errors

Vibration (chatter)

Tool deflection

Temperature change

Run-out

Form Errors

Surface Roughness

Form Error

Ra

Ideal Geometry

SurfaceRoughness

CL

Y

Form Error

X

a. ideal geometry

b. form error

c. surface roughness

20

Taylor’s equation, 𝑉𝑇𝑛= C

V = cutting speed

T = tool life

n, C = Taylor constants (empirical)

f = feed rate, d = depth of cut

𝑉𝑇𝑛= C

𝑙𝑜𝑔𝑉 = 1

𝑛𝑙𝑜𝑔𝑉 +

1

𝑛𝑙𝑜𝑔𝐶

𝑇 =𝑐

𝑣

1

𝑛(f, d: constant)

logV

logT

n

1

C

Tool life-Feed rate (log scale)

21

Cost Estimation

22

More cost estimation

Ostwald model

American Machinist Cost Estimator

Demo

Data for wage

• http://www.kosis.kr/ (통계청)

• http://laborstat.molab.go.kr/ (노동부)

23

Material costs

FOB: freight-on-board, warehouse

24Productive

hour costs

25

DFM: machining

Under cut

26

DFM: machining (2)

27DFM:

machining (3)

28

Including deburring cost

(Dornfeld et al. 2001)

29

Controller

Microscope

Spindle

Main computer

X-Y stage

Vice

Micro Machining System

Tip of 127μm endmill

Micro endmills

Positional resolution : 1 ㎛

Tool diameter : 50 ㎛~1000 ㎛

High speed : 200,000 RPM

Tool material : HSS & TiN coating

Work piece : Metal, Polymer, etc Precision stage

30

1,000

10,000

100,000

0.1 1 10 100

average TiAlN coating

Tool diameter (mm)

Tool Cost (\)

DFM: micro milling

10 mm endmill

10 μm stage error

0.1% for slot cutting

100 μm endmill

10μm stage error

10% for slot cutting

Cost structure of micro

machining is different from

that of macro machining.

Tool cost dominates

A tip is not exact edge in micro scale

31

Spindle run-out

< Total Indicator Reading (TIR) Measurement >

Run-out effect on the final geometry is critical in micro machining

Total run-out = TIR (Total Indicator Reading) + Error Terms

(vibration, thermal deformation, etc)

< Concept of run-out >

< Result of Total Indicator Reading (TIR) >

0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25

Tool length (mm)

Ru

n-o

ut

(㎛)

100㎛

200㎛

32

Micro walls

Barrier ribs

Rib width: 60㎛Height: 500 ㎛Tool: φ200 ㎛

Spindle: 24,000rpm

DOC: 25㎛Feed rate: 100㎛/s

Time: 3hr 28min

×1200 ×600

×100

Geometric error: ~ 5 ㎛ (including error of microscope)

×100

×600 ×600

×300

×300

33

Micro machined mold

0.753mm

0.993mm

1.005mm

1.221mm

34

Micro drilling and milling

PCBs for semiconductor

PCBs for cell phone

Shape of Micro drill

PCB machining micro end mill

4 mm

0.65 mm

1mm Flute length

35

Energy Consumption Model for Micro drilling

Measuring and decomposition of energy consumption of machine tool

Consists of PBASIC (PPERIPHERAL), PSTAGE, PSPINDLE, PMACHINING

PTOTAL = PBASIC + PSPINDLE + PSTAGE + PMACHINING

= PBASIC + (a1 V b1 + c1) + (a2 f b2 + c2) + (T×f + M×V)

(H.S. Yoon, J.S. Moon, M.Q. Pham, G.B. Lee, and S.H. Ahn, paper accepted)

Energy Control ChartPCB drilling configurations

36

Manufacturing Cost Model for Micro drilling

Considering tool wear

Consists of CTOOL, CENERGY, CPERIPHERAL

CTOTAL = n/L × (c 1/γ / (V D α f β) 1/ γ) × CTOOL +

t × (PBASIC + (a1 V b1 + c1) + (a2 f b2 + c2)) × CENERGY + CPERIPHERAL

(H.S. Yoon, J.S. Moon, M.Q. Pham, G.B. Lee, and S.H. Ahn, paper accepted)

Integrated energy consumption during 0~2,000 holes (Integral)Schematic of tool tip wear

37

DFM: end mill wear estimation

High speed spindle (HEN-40 ,Fisher, Swiss)

• Max. 42,000 rpm, Run out <2 mm (TIR)

Precision micro-stage(404150XR , PAKER)

• resolution 1 mm

Programmable multi-axis Controller (PMAC2, Delta Tau Data Systems Inc.)

Milling condition

Cutting speed 60 m/min

Feed rate 0.003 m/min

Fixture

Spindle

Micro-end mill

Workpiece

Vacuum

clamping

Vacuum

valve

38

End mill wear

Unused 1200 mm 2400 mm

X1500

X2400

X1500X1500

X2400X2400

Cutting length

As the milling distance was increased, the wear at cutting blade was greater

REF) Park, J. B., Wie, K. H., Park, J. S., and Ahn, S. H.*, 2009, "Evaluation of machinability in the micro end milling of

printed circuit boards," Proceedings of the Institution of Mechanical Engineers, Part B, Journal of Engineering Manufacture

(England), Vol. 223, No. 11, pp. 1465-1474

39

Ultra-small Micro End Mill

REF) Aurich, Jan. C.*, Reichenbach, Ingo G., Schuler, M. Guido, 2012, "Manufacture and application of ultra-small micro

end mills," CIPR Annals – Manufacturing Technology, Vol. 61, pp. 83-86

SEM pictures of slot milled structures

Micro milled undercut-dovetail structure in PMMA.

Micro end mill

Micro profile end mill

40

Generation of Ion Beam Path: Description

Generation of ion beam path for the improvement of precision and

accuracy: roundness, concentricity and precision of dimension

Illustration of ion beam paths: beam traces by different ion beam

paths using FIB-CVD

Spiral

Raster w/o blanking Serpentine

Offset Spiral

: Scan end

: Scan start

41

Generation of Ion Beam Path: Experimental ResultsRaster scan

Serpentine scan

Offset (in) scan

Offset (out) scan

Spiral (in) scan

Spiral (out) scan

Concentricity Roundnessinner ConcentricityRoundnessouter

Acc

ura

cy (

nm

)

Pre

cisi

on (mm

)

Diameterinner Diameterouter

Accuracies and precision of 2.5D circular pocket

42

Fabrication of 3D microstructure by FIB Characteristics of Continuous Slicing Method

Reduction of material redeposition by spiral scan

Angle dependent cutting enhancement

Variable pixel dwell time method

Slice-by-slice method Continuous slicing method

Depth: 279.54 nm Depth: 295.90 nm

43

DFM: cutting force estimation

Data cable

Vise

X

ZY

Dynamometer

3-axis micro stage

Jig

Workpiece

End mill

Fx

Fz

FyDynamometer

Feed direction

Amplifier dSPACE PC

Dynamometer

44Backstitch tool path

on micro-drilling

Hole misalignment Comparison of the backstitch tool path with a conventional tool path

Method of measuring the positioning

errors for the drilled holes

Moon, J. S., Yoon, H. S., Lee, G. B., and Ahn, S. H., 2014, "Effect of Backstitch Tool Path on Micro-drilling for Printed Circuit Board,"

Precision Engineering - Journal of the International Societies for Precision Engineering and Nanotechnology

45A Comparison of Energy Consumption in Bulk

Forming, Subtractive, and Additive Processes

Yoon, H. S., Lee, J. Y., Kim, H. S., Kim, M. S., Kim, E. S., Shin, Y.J., Chu, W. S., and Ahn, S. H., 2014, "A Comparison of Energy Consumption in Bulk Forming, Subtractive,

and Additiv Processes: Review and Case Study," International Journal of Precision Engineering and Manufacturing - Green Technology, IJPEM - GT

Specific Energy Consumption (SEC) for the

three categories of manufacturing process

SEC versus productivityProduction costs

SEC in terms of number of parts

Energy consumption results for the

case studies

Test geometry

46

Applications of

Subtractive Processes

47

DFM: Micro drilling for biomedical application

Porous hydroxyapatite

Artery wallCalcified deposit

Intimal plaqueFibrous cap

Chronic Total Occlusion (CTO)

Complete obstructions or blockages of an artery

About 50% of severe CVD patients having CTO

(Christofferson et al., Am J Cardiol, 2005)

Success rates of less than 70% for CTO treatment

(Segev and Strauss, J Interven Cardiol, 2004)2008 Nucleus Medical Art, Inc.

Micro drilling test using a porus hydroxyapatite instead of CTO material

48

Blood Vessel Surgery Robot

49

DFM: force, torque, and wear

Tests for 6 different types of

burrs

Drilling speed : 120,000 ± 30,000 RPM

Pressure : 3 kgf/cm2

Flow rate : 15 Liter/min

Feed : 2 mm/sec

Max. depth : 3 mm

Repeat number : 3 times

Test condition : No water

Test specimen : porous hydroxyapatite

Burr 1 Burr 2 Burr 3 Burr 4 Burr 5 Burr 60

2

4

6

8

10

12

14

Burr1 Burr2 Burr3 Burr4 Burr5 Burr6

Z F

orc

e (

N)

50

Surface of the burrs after drilling test

REF) Kim, M. H., Kim, H. J., Kim, N. N., Yoon, H. S. and Ahn, S. H.*, 2011, "A rotational ablation tool for

calcified atherosclerotic plaque removal," Biomedical Microdevice, Springer (Netherlands), Volume 13, No.

6, pp. 963-971

SEM images of the Rotablator burr (left) and a burr with greater-like

microblades (right) (Nakao et al. 2005)

FESEM images of the laser beam-engraved tool surface

51

Spindle

Chuck

Cutting tool Turret

Workpiece

Milling toolTurret

Cutting + Milling

Cutting

CNC Lathe

CNC lathe can achieve multi-functional machining using

attached milling turret, sub-spindle, etc.

52

Precision machining

GMC – Multi spindle Technology

Airbag igniter valve

Camshaft

Usage in Car industry

Stud BoltGMC – Multi spindle Technology

High pressure linkage

Spray nozzlePulley

Joint

GMC – Multi-axis manufactureing

53

Precision machining

Pneumo Diamond Turning Machine

54

Ultraprecision machiningFANUC ROBOnano Ui

55

FANUC ROBOnano α-0iB Ultraprecision machining

56

LASER machining

Light Amplification by Stimulated Emission of Radiation (LASER)

Laser machining

Thermal process, removes mass by concentrating high energy

Small mass removal: cutting, drilling, welding . . .

No tool deflection from the contact → high aspect ratio shape

57

Pulsed Laser

58

Mechanical machining vs. Laser machining

Cutting tool

Feed direction

Removed material

Laser-beam

Feed direction

Mechanical machining Laser machining

Removed material

Interference problem

59

Light guide panel (LGP)

Light guide panel is an element of the LCD back light unit

Design of experiment using Taguchi method

Power, scanning speed, ratio of line gap, and number of line were investigated

The structure of TFT-LCD

60

Design of experimentOrthogonal arrays and experimental results

Laser-machined Light Guide Panel

61

Laser therapy and surgery

LASIK surgery for dry eye syndrome

using laser

Cosmetic surgery: moles, warts,

wrinkles, scars, hairs, tatoos, etc.

Laser therapy can release the pain and heal the body

62

Focused ion beam (FIB) system

Ion gun

Liquid metal ion source (LMIS)

Ion optical column

Electrostatic lens

Scan coil

Stigmator

Specimen chamber

Vacuum system

Utke et al. J. Vac. Sci. Technol. B 26 (4) 2008

Schematics of focused ion beam system

63

Principle of FIB fabrication

Elastic collision (nuclear collision) Dislocation of surface atom by primary ion (PI)

Binary collision (collision cascade)

Inelastic collision (electronic collision) Secondary electron (SE) by PI

SE by inelastic collision

Backscattered electron (BSE) by SE

Initiation of material removal

Excited surface atom (ESA) by nuclear collision

For Si substrate, the binding energy is 2.5 eV

When ion energy is exceed the substrate binding energy,

the excited surface atom will be removed.

Utke et al. J. Vac. Sci. Technol. B 26 (4) 2008

64

FIB technology

Merits

• High throughput, low penetration depth

Hybrid process

• Material destruction & construction

Various material

• Destruction: all solid materials

• Construction: C, W, Pt

Various application

• MEMS/NEMS, SPM tips

• Micro/nanoscale medical devices

• Photonic devices

• Micro/nanoscale mould

Two-tip micro-tool having triangular cutting facetD P Adams Precision Engineering 25 (2001) 107

Nano-fluidic emitter having 21 nm capillary slotsS. Arscott Nanotechnology 16 (2006) 2295

65

Considerations on DFM in FIB

Geometrical and efficiency issues related to DFM in FIB fabrication

REF) Kim, C. S., Ahn, S. H., Jang, D. Y., 2011, "Review: Developments in Micro/Nanoscale Fabrication

by Focused ion beams ," Vacuum, Elsevier (Netherlands), Volume. 86, No. 8, pp. 1014-1035.

66

DFM on FIB (1)

Better surface roughness

Better milling rate

Continuous slicing method

- Milling rate = 1.91 × ions/cm2

2D slice-by-slice method

- Milling rate = 1.81 × ions/cm2

Fabrication method SIM 60 ° tilt view AFM cross-section view

67

DFM on FIB (2)

To have vertical sidewalls

To have bilateral-symmetry

Raster scan routine

- Asymmetry

Spiral scan routine

- Symmetry

W C hopman Nanotechnology 18 (2007) 195305

68

Nano-lathe (나노선반)

Conventional lathe in FIB system

Precision wheel stage attached to

the FIB systemT Fijii J. Micromech. Microeng. 15 (2005) S286

Process outline of nano-lathe

Scanning ion scope image showing the intermediate processing

70

Tool Path Generation

Concept of pocketing

70

71

Tool Path Generation (cont.)

Rough Cutting

Remove bulk material

One type: the raw material has a shape close to the

final shape

Second type: the raw material is provided in the form

of block

< Second type of rough cutting >

< One type of rough cutting >

71

72

Tool Path Generation (cont.)

Finish cutting

Path interval and cups height

Step length and deviation

Generation of CC points and

CL point

< Various cutter paths on a surface >

73

Tool Path Generation (cont.)

Gouging Problem

Choosing a tool whose radius is smaller than the

minimum radius of curvature of the part surface

However, too small tool may result in inefficient

machining

< Gouging of a surface > < Gouging at a neighboring surface >

73

74

Overcut

74

75

Overcut (cont.)

75

76

Area of Cutting

Upward cutting vs. downward cutting

Zero velocity zone may occur

76

77

Deflection of Tool

Undercut vs. overcut

77

78

5-axis Machining

78

79

Selection of tool size

Considering cost and time

0 1 2 3 4

79

80

Conclusion

Material removal

Material removal rate (MRR) is important

Under cut is usually not easy to fabricate

Contact (mechanical machining) vs. non-contact (laser

& FIB)

Direct tool shape transfer: the Gaussian beam shape for laser and FIB

Substrate properties dependency

81

Contact Information

Precision machining

http://nmrc.yonsei.ac.kr/ (EDM)

http://www.sharp-eng.com/web/ (EDM & Machining)

Laser machining

http://nmrc.yonsei.ac.kr/

http://www.laserpix.co.kr/

Focused ion beam

http://nmrc.yonsei.ac.kr/

http://msp.or.kr

http://www.aac.re.kr/index.html